JP2002363720A - Hot-dip Zn-Al-Mg-Si alloy plated steel pipe with excellent corrosion resistance - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a molten Zn-Al- excellent in corrosion resistance.
The present invention relates to a Mg-Si plated steel pipe. SOLUTION: In weight%, Al: 3-20wt%, Mg: 0.1-10w.
t%, Si: 0.01 to 2 wt%, molten Zn-Al with excellent corrosion resistance having a plating layer composed of the balance of Zn and unavoidable impurities
-An Mg-Si alloy-plated steel pipe, which is further coated with an inorganic film made of an inorganic compound or an organic resin film made of an organic resin, or the upset amount of a bead portion at the time of forming a pipe is reduced. By setting it to 5 to 80% of the thickness,
Furthermore, a hot-dip Zn-Al-Mg-Si alloy-plated steel pipe having excellent corrosion resistance can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hot-dip Zn-Al-Mg-Si plated steel pipe having excellent corrosion resistance.

[0002]

2. Description of the Related Art Plated steel pipes having a Zn, Zn-Al alloy plating layer include a pre-plated steel pipe for forming a plated steel sheet into a steel pipe, and a post-plated steel pipe for subjecting a steel pipe to hot-dip after forming. In particular, the former has been widely used because the cost during pipe formation is better than the latter. Pre-plated steel pipes include Zn-plated steel pipe, Zn-5% Al-plated steel pipe, 55% Al-Zn-1.6% Si-plated steel pipe, Al
There are plated steel pipes and the like. In general, bead repair spraying for cutting the vicinity of a weld bead portion and performing Zn or Zn-Al-based spraying thereon is performed. However, even if bead spraying is performed, the sprayed layer has many pores and poor corrosion resistance. Therefore, in JP-A-2000-239818, an appropriate amount of Mg is added to the plating layer, and a Mg-containing Zn-based material having high protection is provided. There is disclosed a technique of a pre-plated steel pipe in which a corrosion product is used to protect and coat a weld portion and to contain Al to improve the corrosion resistance of a plating layer near the weld portion. However, in the heat-affected zone in the vicinity of the bead, deterioration of plating adhesion and corrosion resistance due to the progress of alloying of Fe-Zn and Fe-Al, and embrittlement cracking of the base material portion particularly when increasing strength. Could occur.

[0003]

Therefore, in the present invention,
Molten Zn-Al-Mg-S with excellent pipe forming stability and corrosion resistance
It is an object to provide an i-alloy pre-plated steel pipe and a method for manufacturing the same.

[0004]

Means for Solving the Problems In order to improve the production stability and corrosion resistance of a plated steel pipe, the present inventor has studied a steel component, a hot-dip plating component, and pipe forming conditions, and has studied a specific steel component and a specific plating composition, It has been found that an alloy-coated steel pipe having excellent corrosion resistance can be obtained depending on manufacturing conditions. The present invention has been completed based on this finding, and the gist of the invention is as follows.

(1) Al: 3 to 20% by weight, Mg: 0.1% by weight
-10% by weight, Si: 0.01-2.0% by weight, the balance of Zn and unavoidable impurities.
n-Al-Mg-Si alloy plated steel pipe. (2) By weight%, Al: 3 to 20 wt%, Mg: 0.1 to 10 wt%, Si:
0.01 to 2 wt%, furthermore, 0.01 to 2% of one or more kinds of Ti, Sn, Ni, and Cr, 0.01 to 2%, and a molten Zn-Al having excellent corrosion resistance and having a plating layer consisting of a balance of Zn and unavoidable impurities.
-Mg-Si alloy plated steel pipe. (3) Molten Zn-Al- having excellent corrosion resistance, having a Ni layer below the plating layer of (1) or (2) in an amount of 0.1 to 10 g / m ² .
Mg-Si alloy plated steel pipe. (4) By weight%, C: 0.01-0.2%, Si: 0.001-1.0%, M
n: 0.01 to 2.5%, P: 0.001 to 0.04%, S: 0.001 to 0.05%, A
l: 0.005 to 0.1%, N: 0.001 to 0.1%, or 0.01% Nb
A hot-dip Zn-Al-Mg-Si plated steel pipe having excellent corrosion resistance, having a plating layer according to (1) or (2) or (3) on the surface of a steel sheet comprising 0.1%, the balance being Fe and unavoidable impurities. (5) At the time of forming the plated steel pipe according to the above (1), (2), (3), or (4), Zn or Zn-A
l-based metal sprayed molten Zn-Al with excellent corrosion resistance
-Mg-Si alloy plated steel pipe. (6) On the plating layer of the plated steel pipe according to (1), (2), (3), or (4), or (5),
Furthermore, an inorganic film composed of an inorganic compound is applied at 70 mg / m ² to 2
000 mg / m ² , characterized by having excellent corrosion resistance
n-Al-Mg-Si alloy plated steel pipe. (7) On the plated layer of the plated steel pipe according to the above (1), (2), (3), (4), (5), or (6), further comprising an organic resin. the organic resin film, 100 mg / m ² melt Zn-Al-Mg-Si alloy steel pipe having excellent corrosion resistance, characterized in that it comprises 2000 mg / m ^2. (8) Up of the bead portion at the time of forming the plated steel pipe according to (1), (2), (3), (4), (5), (6), or (7). A hot-dip Zn-Al-Mg-Si alloy-plated steel pipe excellent in corrosion resistance, characterized in that the set amount is 5 to 80% of the plate thickness.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The reasons for limiting the components of a plating layer will be described. Mg in the plating layer has an effect of improving the corrosion resistance. If it is less than 0.1%, the effect cannot be obtained. On the other hand, if it exceeds 10%, the plating bath is oxidized by contact with the atmosphere, and the black oxide is formed. (Dross) is generated and plating production becomes difficult.

[0007] Al in the plating layer forms an insoluble corrosion product and has an effect of improving corrosion resistance. To achieve this effect, 3% or more of Al is required.
If it exceeds 0%, at the time of welding, an Fe-Al intermetallic compound is locally generated at the interface between the plating layer near the bead portion and the steel base, which impairs the plating adhesion. Therefore, Al is 3 to 20.
%.

[0008] Si in the plating layer is an important element in the present invention. When producing a plated steel pipe using a plated steel sheet, resistance welding is generally performed in many cases. At this time, the welded portion is locally melted, the plating on that portion is evaporated, and the steel is oxidized. The plating layer in the vicinity of the oxidized part is melted, and a reaction with the base iron and oxidation occur. If the Si content is less than 0.01%, (1) the reaction with the iron-plating proceeds, and the plating adhesion deteriorates. (2) Corrosion resistance due to the formation and oxidation of Fe-Al and Fe-Zn alloys (3) When a high-strength steel pipe is formed, there is a possibility that molten zinc embrittlement cracks may occur from the heat-affected zone. (4) In the case of thermal spraying after plating, plating near the sprayed area Various problems occur, such as local melting and alloying of the layer, resulting in deterioration of adhesion and corrosion resistance, and a highly corrosion-resistant plated steel pipe cannot be stably obtained. (5) From the viewpoint of corrosion resistance, Si has the effect of mixing with Mg in the corrosion product of Zn and flowing out in the form of a Mg-Si compound into the welded or sprayed portion, covering the surface thereof and protecting the base. It is necessary to add 0.01% or more. On the other hand, if the Si content exceeds 2%, this effect is saturated, and the plating bath dross increases in the production of plated steel materials.

One, two or more of Ti, Ni, Sn, and Cr are added as necessary to improve corrosion resistance.
If it is less than 0.01%, there is no effect of improving corrosion resistance, and if it exceeds 2.0%, the effect of improving corrosion resistance is saturated.
2.0%.

[0010] The Ni layer below the plating layer is provided as necessary to improve plating adhesion.
Is less than / m ^2, not excellent coating adhesion, the effect of addition exceeding 10 g / m ² saturates.

Next, steel components will be described. C is an element necessary for securing high strength. If it is less than 0.01%, the required strength cannot be obtained, and the decarburization cost increases. On the other hand, if the content exceeds 0.2%, the workability deteriorates and embrittlement cracking after pipe formation is likely to occur.
0.2%.

[0012] Si is a deoxidizing agent in the steel smelting process and is effective as a solid solution strengthening element for strengthening the steel. However, it causes scale flaws during hot rolling. It also has an adverse effect on the surface quality of the rolled
Since it is economically difficult to make it less than 1%, 0.0%
01-1.0%.

Mn is effective as a solid solution strengthening element for strengthening steel, and is added for preventing hot brittleness due to S. However, if it is less than 0.01%, there is no effect, and 2.5%
If it is more than 0.01%, the cost may be increased.
5%. P is an element that affects the strength and the workability. However, if it exceeds 0.04%, the brittleness and the workability are significantly deteriorated, and if it is less than 0.001%, there is no significant effect. 001 to 0.04%.

Although S is inevitably included,
If it exceeds 0.05%, the surface is deteriorated due to hot embrittlement, and if it is less than 0.001%, the effect is small and the desulfurization cost is increased. Al
Is added for deoxidation and denitrification, but if it is less than 0.005%, there is no effect, while if it exceeds 0.1%, there is a risk of nozzle clogging in the steel making process, and the surface properties of the product Is deteriorated, so that the content is set to 0.005 to 0.1%.

[0015] N is desirably small because solid solution N causes stretcher strain and deteriorates the surface properties. When N exceeds 0.1%, the effect becomes significant. However, since it is industrially difficult to reduce the content to less than 0.001%, the content is set to 0.001 to 0.1%.

Nb is added as needed to strengthen the steel. If added, it must be at least 0.01% or more. If it exceeds 0.1%, embrittlement cracking is likely to occur.

Next, the manufacturing method will be described. Steel production method, hot rolling, and pickling may be performed by a normal method,
Of course, there is no problem even if a hot-rolled pickling material, a cold-rolled material, or a material subjected to electric cleaning is used. The present technology can be applied to plating without depending on a manufacturing method such as a Sendzimir type, a flux type, and a pre-plating type. There is no particular problem if an aqueous or organic post-treatment is performed on the plated steel sheet thus produced. This may be performed before pipe formation, after pipe formation, or both.

Further, on the plated layer after plating, Mg,
By coating at least one or more inorganic oxides selected from oxides of Zr, Mo, Ce, Ca, V, and Ti, the corrosion resistance can be further improved. In this case, there is no problem in forming a composite oxide such as a sulfate, a nitrate, a phosphate, and an ammonium salt. When the sum of these is less than 70 mg / m ² , the effect of improving corrosion resistance is small.
If these sum exceeds 2000 mg / m ^2, the corrosion resistance improvement effect is in the range of 70mg / m ² ~2000mg / m ² so saturated.

Alternatively, the corrosion resistance can be improved by coating an organic resin film instead. Adhesion amount of the coating is less than 100 mg / m ^2, the effect is small, the corrosion resistance improving effect exceeds 2000 mg / m ² is in the range of 100mg / m ² ~2000mg / m ² so saturated. The organic resin may be in any form of a water-based resin, a solvent-based resin, a powder-based resin, or a solventless resin. The term "aqueous resin" used herein includes not only a water-soluble resin but also a water-insoluble resin (water-dispersible resin) which is inherently water-insoluble but can be finely dispersed in water such as an emulsion or a suspension. . The resin that can be used as the organic resin is not particularly limited, but includes a polyolefin resin, an acrylic olefin resin, a polyurethane resin, an acrylic resin, a polycarbonate resin, an epoxy resin, a polyester resin, an alkyd resin, and a phenol resin. Resins and other heat-curable resins can be exemplified, and it is more preferable that the resin be crosslinkable. The organic resin may be used as a mixture of two or more or a copolymer. If necessary, a crosslinking agent such as various melamine resins and amino resins may be added.
There is no problem in adding fine silica or a lubricant in addition to the organic resin. Of course, there is no problem in performing various chromate treatments. These treatments improve scratch resistance and slidability.

The coating methods for forming these inorganic oxide or organic films include spray, curtain,
Any method such as a flow coater, a roll coater, a bar coater, brush coating, dipping, and air knife drawing may be used. The final baking temperature is 80-250 ° C.
It is desirable that If the temperature is lower than 80 ° C., the water in the paint is difficult to completely volatilize, so that the corrosion resistance is lowered. If the temperature is higher than 250 ° C., the alkyl portion of the organic resin undergoes denaturation such as thermal decomposition or the film hardens too much. It is not preferable because corrosion resistance and workability are reduced. 70-160 ° C is more preferred. The drying equipment is not particularly limited, but a method using hot air blowing, an indirect heating method using a heater, a method using infrared rays, a method using induction heating, and a method using these in combination can be adopted. In addition, depending on the type of the organic resin used, the resin can be cured by energy rays such as ultraviolet rays and electron beams. In addition, temper rolling may be performed.

Next, regarding pipe making, electric pipe welding, electric resistance welding such as high frequency welding, arc welding, laser welding and the like can be applied. It is important to set the upset amount to 5 to 80% of the sheet thickness at the time of pipe making in order to prevent plating embrittlement cracking at the time of pipe making, and the upset amount is less than 5% or exceeds 80%. However, stable pipe making cannot be performed.

Performing thermal spraying on the bead portion at the time of pipe making further improves the effect of the present invention. That is, in the normal plating, the thermal spraying of the thermal spraying portion is not uniform, so that the plating adhesion and corrosion resistance are not sufficient especially in the vicinity of the boundary with the pre-plating layer, but in the plating layer of the present invention, the Si contained in the plating layer Suppresses excessive alloying between the base iron and the plating, and exhibits excellent corrosion resistance in combination with the effect of improving the corrosion resistance of Mg.
As the thermal spray metal, a conventionally used metal such as Zn or Zn-Al can be used. In particular, a sprayed wire similar to the Al content (3% Al to 20% Al) in the plating layer particularly improves the corrosion resistance.

Further, as described above, various post-treatments can be performed after pipe formation without any problem to improve the corrosion resistance.

[0024]

EXAMPLES [Example 1] Steel slabs shown in Table 1 were melted and plated steel sheets were produced in a usual manner. Tables 2 to 5 show the levels. The steel type No. indicates the steel No. in Table 1. The plating was performed by annealing and plating in a continuous hot-dip plating line of Sendzimir type. The thickness is from 1 mm to 3.2 mm. The annealing atmosphere was 10% hydrogen and residual nitrogen gas, and the dew point was -2.
The temperature was set to 0 ° C. The annealing temperature is 720 ° C and the annealing time is 3-5 minutes. The plating bath compositions are shown in Tables 2-5. The coating weight was 80 g / m ² . The post-treatment after the plating was carried out as required by chromate treatment, inorganic post-treatment, and organic post-treatment shown in Tables 2 to 5. The steel pipe was made by high frequency welding, the outer diameter was 28.6 to 54 mm, and the upset amount was 40%. The upset amount is expressed by the ratio of the height of the peak of the plated molten portion immediately after pipe formation to the plate thickness. Thermal spraying was performed as needed. The thermal spray alloy is a Zn-Al alloy.

The plating adhesion after pipe making was determined by conducting a flattening test described in JIS G 3474, and visually observing plating peeling near the welded portion. ○ indicates that there was no peeling of the plating and that it passed. X indicates the occurrence of peeling and is unacceptable. The appearance was visually inspected for scratches on the steel pipe surface. ○ indicates that there is no problem in appearance and that it passes. × indicates poor appearance and rejection. For corrosion resistance, a composite corrosion test was performed.
The cycle is (1) salt spray (JIS Z 2371 compliant: 5%
NaCl, 35 ° C) 3 hours, (2) drying (60 ° C, relative humidity 30%)
This is a test in which one cycle is 3 hours and (3) 3 hours of wet (50 ° C., 98% relative humidity). The steel pipe test piece was cut out by a length of 130 mm, and both end faces were painted and sealed. The test piece is JIS
According to H 8502, the sample was tested with the weld tilted 20 degrees to the vertical and the welds sideways. This was performed for 100 cycles, and the test was performed by comparing the test piece without Si in the plating layer and the area ratio of red rust generation in the vicinity of the welded portion for each plate thickness and pipe diameter. X is a reference test piece, and is a comparative example in which plating adhesion is poor and red rust is often generated due to the influence of plating alloy. Δ indicates that the area ratio of red rust occurrence exceeds 50% as compared with the standard. ○
Is more than 30% and less than 50%, ◎ is more than 10% and 30%
The following, ◎◎, is less than 10%,
○, ◎, ◎◎ are passed.

As shown in Tables 2 and 3, with no thermal spraying, No. 1 to No. 64 are examples of the present invention. Nos. 65 to 70 are comparative examples. In No. 65, the Al in the plating layer is too high, an Fe-Al intermetallic compound is generated during welding, and the plating adhesion after pipe making deteriorates, so that the corrosion resistance is poor. No66 is Mg in the plating layer
Is too high, dross-like substances adhere to the plating, and the appearance after pipe formation is significantly poor. In No. 67, the dross-like substance adhered to the plating due to the Si in the plating layer being too high, and the appearance after pipe formation was poor. No
From No. 68 to No. 70, there is no Si in the plating layer, the plating adhesion near the welded portion after pipe making is poor, and the corrosion resistance is poor.

As shown in Tables 4 and 5, No. 71 to No. 141 are examples of the present invention. No 142 to No
Up to 145, there is no Si in the plating layer, poor plating adhesion near the weld after pipe making, and poor corrosion resistance.

Example 2 A steel slab shown in Table 1 was melted and a plated steel sheet was manufactured by an ordinary method. The test levels are shown in Tables 6-9. Steel type No. indicates the steel No. in Table 1. Plating was performed by annealing and plating in a continuous pre-plating type pickling and hot-dip plating line. Sheet thickness is from 1.6mm to 8.5
mm hot-rolled material. The annealing atmosphere was 1% hydrogen and residual nitrogen gas, and the dew point was -20 ° C. Annealing temperature is 450 ° C and annealing time is 3-5 minutes. The plating bath compositions are shown in Tables 6-9. The coating weight was 80 g / m ² . Post-treatment after plating is shown in Tables 6 to 9, chromate treatment, inorganic post-treatment,
Organic work-up was performed as needed. Pipe forming to steel pipe is high frequency welding, the outer diameter is 25.4-114.3 mm,
The upset amount was set to 50%. The upset amount is expressed by the ratio of the height of the peak of the plated molten portion immediately after pipe formation to the plate thickness. Thermal spraying was performed as needed. The thermal spray alloy is a Zn-Al alloy.

The plating adhesion after pipe making was determined by conducting a flattening test described in JIS G 3474, and visually observing plating peeling near the welded portion. ○ indicates that there was no peeling of the plating and that it passed. × indicates rejection due to peeling. The appearance was visually inspected for scratches on the steel pipe surface. ○
Has passed without any problem in appearance. × indicates poor appearance and rejection. For corrosion resistance, a composite corrosion test was performed. The cycle is (1) salt spray (based on JIS Z 2371: 5% NaCl,
This is a test in which one cycle consists of 3 hours at (35 ° C.), 3 hours at (2) dry (60 ° C., 30% relative humidity), and 3 hours at (3) wet (50 ° C., 98% relative humidity). The steel pipe test piece was cut out by a length of 130 mm, and both end faces were painted and sealed. The test piece is JIS H
According to 8502, tilt the sample by 20 degrees with respect to the vertical direction,
The test was performed with the weld facing sideways. This was carried out for 100 cycles, and the test was conducted by comparing the test pieces having no Si in the plating layer and the area ratio of red rust generation in the vicinity of the welded portion for each plate thickness and pipe diameter. X is a reference test piece, and is a comparative example in which plating adhesion is poor and red rust is often generated due to the influence of plating alloy. Δ indicates that the area ratio of red rust occurrence exceeds 50% as compared with the standard. ○ is 3
More than 0% and 50% or less, ◎ is more than 10% and 30% or less, ◎◎ is less than 10%, ○,
◎, ◎◎ are acceptable.

As shown in Tables 6 and 7, No. 146 to No. 209 are examples of the present invention without thermal spraying. No210 to N
Up to o220 are comparative examples. In No. 210, the Al in the plating layer was too high, and an Fe-Al intermetallic compound was generated during welding, and the plating adhesion after pipe making deteriorated, so that the corrosion resistance was poor. No211
In the case of Mg, the Mg in the plating layer is too high, and dross-like substances adhere to the plating, and the appearance after pipe formation is significantly poor. In No. 212, the dross-like substance adhered to the plating due to the Si in the plating layer being too high, and the appearance after pipe formation was poor. Nos. 213, 215, 217, and 219 have no Si in the plating layer, have poor plating adhesion near the welded portion after pipe making, and have poor corrosion resistance. In Nos. 214, 216 and No. 218, the Ni plating thickness of the lower layer of the plating layer was too thin, and the plating adhesion after pipe making was poor.

As shown in Tables 8 and 9, No. 221 to No. 289 are examples of the present invention. No290 to N
Up to o300 are comparative examples. In No.290, the Al in the plating layer is too high, and an Fe-Al intermetallic compound is generated at the time of welding, and the plating adhesion after pipe formation deteriorates, so that the corrosion resistance is poor. No291
In the case of Mg, the Mg in the plating layer is too high, and dross-like substances adhere to the plating, and the appearance after pipe formation is significantly poor. In No.292, the dross-like substance adhered to the plating because the Si in the plating layer was too high, and the appearance after pipe formation was poor. No. 293, No. 295, No. 297, and No. 299 have no Si in the plating layer, have poor plating adhesion near the welded portion after pipe making, and have poor corrosion resistance. In Nos. 294, No. 296, No. 298, and No. 300, the Ni plating thickness below the plating layer was too small, and the plating adhesion after pipe making was poor.

Example 3 Steel slabs shown in Table 1 were melted and plated steel sheets and steel pipes were produced in a usual manner. The test levels are shown in Tables 10 and 11. Steel type No. indicates the steel No. in Table 1. The plating was performed by annealing and plating in a continuous hot-dip plating line of a Sendzimir type or a pre-plating type. The sheet thickness is 2.3 mm hot-rolled material. The annealing atmosphere is a 10% hydrogen and residual nitrogen gas atmosphere for the Sendzimir type, and a 1% hydrogen and residual nitrogen gas atmosphere for the pre-plating type.
The dew point was -30 ° C. The annealing temperature is 730 ° C for the Sendzimir type, 450 ° C for the pre-plating type, and the annealing time is 3 to 5 minutes, respectively. The coating weight was 80 g / m ² .
The steel pipe was formed by high frequency welding, the outer diameter was 42.7 mm, and the upset amount was 3 to 85%.

[0033] Cracking after pipe forming was performed by performing a flattening test described in JIS G 3474, and visually observing cracks in the base metal near the welded portion. ○ indicates that there was no crack in the base material and the test was passed.
X indicates occurrence of base material cracking, and is unacceptable. The appearance is
The surface of the steel pipe was visually inspected for scratches. ○ indicates that there is no problem in appearance and that it passes. × indicates poor appearance and rejection.

No. 301 to No. 340 are examples of the present invention, and have good weld cracks and good appearance. No. 341 to No. 345 have too small upset amount and cannot be welded normally. From No. 346 to No. 350, the upset amount was too large, causing embrittlement cracking. No. 351 has an excessively high C content and causes embrittlement cracking. No. 352 has too high Si and scale flaws remain even after pipe production, resulting in poor appearance. In No. 353, Mn is too high, causing embrittlement cracking. In No. 354, P was too high, causing embrittlement cracking. In No. 355, S was too high and embrittlement cracking occurred. No356
In Al, the Al content is too low and the N content is high. In No. 357, Nb is too high, causing embrittlement cracking.

[0035]

[Table 1]

[0036]

[Table 2]

[0037]

[Table 3]

[0038]

[Table 4]

[0039]

[Table 5]

[0040]

[Table 6]

[0041]

[Table 7]

[0042]

[Table 8]

[0043]

[Table 9]

[0044]

[Table 10]

[0045]

[Table 11]

[0046]

As described above, the plated steel pipe obtained by the present invention can be used for civil engineering and construction materials such as signboard supports, road sign supports, windbreak fences, square pipes, resin-coated steel pipes, greenhouses and floor ducts, and the like. It is useful as a housing application such as a conduit tube, or as an automobile member such as a muffler and a lower member.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) C22C 38/00 301 C22C 38/00 301Z 38/06 38/06 38/12 38/12 C23C 2/38 C23C 2/38 4/08 4/08 28/00 28/00 B 30/00 30/00 C (72) Inventor Akira Takahashi 1 Kimitsu, Kimitsu City, Chiba Prefecture Inside the Nippon Steel Corporation Kimitsu Works (72) Inventor Hajime Onozawa 1 Kimitsu, Kimitsu City, Chiba Pref., Nippon Steel Corporation Kimitsu Works (72) Inventor Kenichi Asai, 2-6-3 Otemachi, Chiyoda-ku, Tokyo Nippon Steel Corporation (72) Invention Person Hidetoshi Nitoka 1 Fujimachi, Hirohata-ku, Himeji-shi, Hyogo Nippon Steel Corporation Hirohata Works (72) Inventor Hideki Hamaya 20-1 Shintomi, Futtsu-shi, Chiba Nippon Steel Corporation Technology Development Division F Term (reference) 4D075 BB83X BB87X BB91X BB92Z CA13 CA33 DA06 DA15 DA20 DB05 DC01 DC05 DC13 EA02 EA06 EA07 EA09 EA13 EB01 EB13 EB22 EB32 EB33 EB35 EB36 EB38 EB45 4K027 AA07 AA23 AB02 AB05 A26 EB04 A03 AB03 A03 CB04 BA21 BB04 BB05 BB11 BC02 BC05 CA11 CA24

Claims (8)

[Claims] 1. Al: 3 to 20% by weight, Mg: 0.1 to 10% by weight
t%, Si: 0.01 to 2 wt%, molten Zn-Al with excellent corrosion resistance having a plating layer composed of the balance of Zn and unavoidable impurities
-Mg-Si alloy plated steel pipe. 2. In weight%, Al: 3-20 wt%, Mg: 0.1-10 w
t%, Si: 0.01 to 2 wt%, and further contains 0.01 to 2% of one or more of Ti, Sn, Ni, and Cr and has a plating layer composed of Zn and unavoidable impurities, and has excellent corrosion resistance. Molten Z
n-Al-Mg-Si alloy plated steel pipe. 3. The method according to claim 1, wherein the plating layer is Ni.
Molten Zn-Al with excellent layer in corrosion resistance having 0.1 to 10 g / m ²
-Mg-Si alloy plated steel pipe. 4. C: 0.01 to 0.2%, Si: 0.001 to 1% by weight
%, Mn: 0.01 to 2.5%, P: 0.001 to 0.04%, S: 0.001 to 0.05
%, Al: 0.005 to 0.1%, N: 0.001 to 0.1%, or even N
b: A hot-dip Zn-Al-Mg-Si plated steel pipe having excellent corrosion resistance, comprising a plating layer according to claim 1 on the surface of a steel sheet comprising 0.01 to 0.1%, balance Fe and unavoidable impurities. 5. A molten Zn—Al—Mg—S that is excellent in corrosion resistance by performing Zn or Zn—Al-based metal spraying at the time of forming the plated steel pipe according to claim 1, 2, 3, or 4.
i-alloy plated steel pipe. 6. An inorganic film made of an inorganic compound is further provided on the plated layer of the plated steel pipe according to claim 1, or 2, or 3, or 4, or 5 to 70 mg / m ^{2 to} 2000 mg / m ^2. Fused Zn-Al-Mg excellent in corrosion resistance characterized by having
-Si alloy plated steel pipe. 7. An organic resin film composed of an organic resin is further provided on the plated layer of the plated steel pipe according to claim 1, or 2, or 3, or 4, or 5, or 6, further comprising 100 mg / m ^2.
A hot-dip Zn-Al-Mg-Si alloy-plated steel pipe excellent in corrosion resistance, characterized by having a content of 2,000 mg / m ² . 8. The upset amount of a bead portion at the time of forming a plated steel pipe according to claim 1, or 2, or 3, or 4, or 5, or 6, or 7, is 5 to 80% of the plate thickness. Zn-Al-Mg-Si with excellent corrosion resistance
Alloy plated steel pipe.